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Solids are a state of matter in which the constituent particles are packed together very closely. Solids have a very high intermolecular force due to the low intramolecular distance. They do have a rigid shape and are incompressible. Solids have fixed volume, size, and shape. The particles that make up a solid item are set in place and cannot freely move. For the components of solids, only motion along the mean position is possible.
Based on the type of order inherent in the arrangement of their constituent particles, solids can be categorized as crystalline and amorphous solids. Crystalline solids are anisotropic, have a high melting temperature, and have their component particles arranged in a long-range order. Since the organization of the component particles is short-range ordered, isotropic, and lacks a clearly defined melting temperature, amorphous solids behave like icy liquids.
Important MCQs on The Solid State for the students to test their knowledge on the given topic.
Ques 1. A crystalline solid:
- Changes abruptly from solid-state to liquid upon heating
- Has no definite melting point.
- Undergoes deformation of its geometry easily
- Has irregular 3-dimensional arrangements.
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Explanation: Even when heated, they do not undergo geometric deformation. Over a range of temperatures, they don't become softer. In actuality, when heated to their melting point, crystalline solids quickly transform from solid to liquid.
Ques 2. What will be the ratio of the number of atoms present in a simple cubic, body-centred cubic and face-centred cubic structure respectively?
- 8:1:6
- 1:2:4
- 4:2:1
- 4:2:3
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Ans. (B) 1:2:4
Explanation: The basic cube has eight atoms at each corner, the body-centred cube has one atom in the middle of the body and the face-centred cube has eight atoms at each corner and six atoms in the centre of each face. Each atom in the corner contributes 1/8, while each atom in the face's centre contributes 1/2. Now it is straightforward to determine the ratios of a body-centred cubic, a face-centred cubic, and a basic cube.
Ques 3. Na and Mg crystallize in crystals of bcc and fcc form respectively and then the amount of Na and Mg atoms present in their respective crystal unit cells is:
- 4 and 2
- 9 and 14
- 14 and 9
- 2 and 4
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Ans. (D) 2 and 4
Explanation: Eight atoms are located at the corners of the bcc cell, with one atom in the middle. The fcc cell has one atom on each of the six sides and eight atoms at each of the eight corners. Two unit cells share the atom at the face.
Ques 4. How many unit cells are divided equally in a face-centred cubic lattice?
- 2
- 4
- 6
- 8
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Ans. (C) 6
Explanation: It is evenly shared by 6 unit cells since the F.C.C. unit cells have 6 faces.
Ques 5. When is the Schottky defect in a crystal observed?
- When the ion leaves its normal position and then, occupies an interstitial location
- When the unequal number of cations and anions is missing from the lattice
- When the density of the crystal increases
- When an equal number of cations and anions are missing from the lattice
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Ans. (D) An equal number of cations and anions are missing from the lattice.
Explanation: When the lattice is missing an equal amount of cations and anions, this is known as a Schottky defect. The electrical neutrality of the crystal will be impacted if there are not an equal amount of missing cations and anions.
Ques 6. What is the total number of voids in 0.5 mol of a compound forming hexagonal close-packed structure?
- 6.022 × 1023
- 3.011 × 1023
- 9.033 × 1023
- 4.516 × 1023
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Ans. 9.033 × 1023
Explanation: Z eff for HCP electrons = 6
Number of the unit cells in HCP = 0.5/6 × 6.022 ×1023
= 6.022 ×1023 / 12
There are 12 tetrahedral and 6 octahedral voids in a single unit cell. 18 total voids (in one unit cell)
Total Number of Voids = 18 × 6.022 ×1023/12 = 9.033 × 1023
Ques 7. The axial ratios for the orthorhombic system are a ≠ b ≠ c, what will be the axial angles?
- α = β = γ ≠ 90
- α ≠ β ≠ γ ≠ 90
- α = β = γ = 90
- α ≠ β ≠ γ = 90
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Ans. (C) α = β = γ = 90
Explanation: For the orthorhombic system, axial ratios are a ≠b≠ c and the axial angles are α=β=γ=90. Thus, all three edge lengths are unequal but all the angles are equal. They are equal to 90 degrees.
Ques 8. In NaCl structure
- All octahedral and tetrahedral sites are occupied
- Only octahedral sites are occupied
- Only tetrahedral sites are occupied
- Neither octahedral nor tetrahedral sites are occupied
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Ans. (B) Only octahedral sites are occupied
Explanation: Chlorine ions are found in every part of the NaCl molecule. The octahedral voids, on the other hand, are occupied by sodium ions. We can observe that in the structure, every octahedral vacuum is filled. We may infer from these facts that only octahedral sites are occupied in the NaCl structure.
Ques 9. Why do the Alkali halides not display or show the Frenkel defect?
- Anions and Cations have almost equal sizes
- There is a large difference in the size of cations and anions
- Anions and Cations have a low coordination number
- Anions cannot be accommodated in voids
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Ans. (A) Anions and Cations have almost equal sizes
Explanation: Because cations and anions are almost the same size and cannot fit in interstitial locations, alkali metals do not exhibit the Frenkel defect.
Ques 10. Silver halides generally show
- Schottky defect
- Frenkel defect
- Both Frenkel and Schottky defects
- Cation excess defect
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Ans. (C) Both Frenkel and Schottky defects
Explanation: Due to the strong ionic nature of silver halides, the Schottky defect is conceivable. So, option C is the right response. As an illustration, AgBr exhibits the Schottky and Frenkel defects. Ions absent from their lattice point cause the Schottky defect while missing ions occupying interstitial sites cause the Frenkel defect.
Ques 11. The effect of the Frenkel defect on the density of ionic solids is that
- The density of the crystal increases
- The density of the crystal decreases
- The density of the crystal remains unchanged
- There is no relationship between the density of a crystal and the defect present in it.
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Ans. (C) The density of the crystal remains unchanged
Explanation: The Frenkel defect does not affect the density of ionic solids. This flaw simply causes the ions to move within the crystal, preserving both the volume and mass, hence it does not affect the solid's density.
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